JP4132898B2 - Dry cleaning method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dry cleaning method and a dry cleaning substrate, and more particularly to a dry cleaning method and a dry cleaning substrate applied to a dry etching apparatus.
[0002]
[Prior art]
In the semiconductor manufacturing process, there are processes for etching various thin films and the like, and a dry etching apparatus is mainly used. In this dry etching apparatus, plasma is generated by applying high frequency power to an etching gas introduced to remove an unnecessary film, and the etching gas is activated to react with the film to perform etching. is there.
[0003]
The reaction product between the etching gas and the object to be etched is not completely volatilized and exhausted from the chamber, and a part of the reaction product adheres to the low temperature part of the chamber or enters the plasma and is recycled. It decomposes and becomes a low vapor pressure, adheres in the chamber and becomes a deposit.
[0004]
In particular, in the process of forming a ferroelectric capacitor of a semiconductor memory using, for example, a ferroelectric capacitor, the object to be etched is a Pt film, a PZT film or an IrO. _X Since the reaction product of these films and the etching gas is low in volatility because it is made of a film such as a film, it is necessary to perform etching mainly by sputtering reaction. Therefore, deposits are deposited in the chamber compared to other etching processes. Is easy to adhere.
[0005]
Not only does the generation of plasma become unstable or the etching rate fluctuates due to the influence of the deposit, but the deposit peels off from the chamber and becomes particles, which greatly affects the manufacturing yield of the semiconductor device.
[0006]
For this reason, in the mass production process, the number of particles in the chamber increases with the number of processed sheets, and after reaching the empirically set number of processed sheets, SF is not opened to the atmosphere without opening the chamber to the atmosphere. ₆ The deposits are removed by generating a plasma of a cleaning gas. Then, after a predetermined number of lots have been processed for a longer time, the chamber is opened to the atmosphere and the chamber is wet cleaned using chemicals or the like.
[0007]
By the way, in recent years, a dry etching apparatus applies high frequency power to a plasma generating coil in place of a parallel plate RIE apparatus, and also applies bias power to the substrate to be etched to generate plasma to perform etching. Devices of the type to perform (eg ICP etc.) are becoming widely used.
[0008]
In this type of dry etching system, when dry cleaning is performed, plasma is simply applied by applying high frequency power to the plasma generating coil without applying bias power so that the cleaning plasma sufficiently circulates in the chamber. Was generated and dry cleaning was performed.
[0009]
Furthermore, in an etching apparatus using an electrostatic chuck as a means for fixing the substrate to be etched, a silicon substrate, a quartz substrate, or the like is placed on the electrostatic chuck so that the electrostatic chuck is not damaged by being exposed to plasma. The dry cleaning was performed with the electrostatic chuck protected from plasma.
[0010]
[Problems to be solved by the invention]
However, when the above silicon substrate or quartz substrate is placed on an electrostatic chuck and dry cleaning is performed, the silicon or quartz easily reacts with the plasma of the cleaning gas (halogen gas such as fluorine gas) and is etched. Therefore, the reaction product may accumulate in the chamber and cause particles to be generated.
[0011]
In addition, since the cleaning gas is actively reacted with the silicon substrate or the quartz substrate and consumed, the cleaning rate of the deposits adhering to the chamber decreases, and as a result, the time required for dry cleaning becomes longer. There is.
[0012]
To solve these problems, alumina (Al ₂ O _Three There is a method of performing dry cleaning using a substrate that is not easily etched by plasma of a cleaning gas such as a substrate. JP-A-9-330885 describes that a ceramic substrate such as an alumina substrate is used for the purpose of protecting the susceptor when the chamber of the CVD apparatus is cleaned.
[0013]
However, when dry cleaning is performed by placing an alumina substrate on an electrostatic chuck, a reaction product of the alumina substrate and the cleaning gas is newly deposited in the chamber, unlike a silicon substrate or a quartz substrate. Although the problem of becoming a particle source is solved, there is a problem that deposits easily adhere to the alumina substrate to be removed in the chamber. This problem is particularly noticeable in the process of forming the above-described ferroelectric capacitor, for example.
[0014]
For this reason, when the alumina substrate is unloaded from the chamber after dry cleaning, or when the load lock chamber is opened to the atmosphere in order to take the alumina substrate to the outside, the deposits re-adhered on the alumina substrate are removed from the chamber There is a possibility of causing particles by scattering into the load lock chamber.
[0015]
Therefore, the number of particles counted does not become less than the standard value in spite of the dry cleaning, so that the efficiency is low such as performing cleaning again, which causes a decrease in the apparatus operating rate.
[0016]
The present invention has been made in view of the above problems, and a dry cleaning method capable of sufficiently suppressing the generation of particles and performing cleaning in a shorter time, and a dry cleaning used in the method. An object of the present invention is to provide a circuit board.
[0017]
[Means for Solving the Problems]
In order to solve the above problem, the present invention relates to a dry cleaning method, and a high frequency power for plasma generation and a bias for a predetermined gas atmosphere high frequency A dry cleaning method of a dry etching apparatus of a type in which plasma is generated by applying power and etching, and at least a dry cleaning substrate in which a portion exposed to plasma is made of alumina or silicon carbide Placed on the substrate placement part in the chamber of the apparatus, introduced a first cleaning gas into the chamber, First Applying the plasma generating high frequency power and the bias high frequency power to generate the plasma to perform a first dry cleaning, After performing the first dry cleaning, a second dry cleaning is performed with a plasma of a second cleaning gas different from the first dry cleaning gas. In the second dry cleaning, the second plasma generation is performed. Apply high-frequency power for bias, do not apply high-frequency power for bias It is characterized by that.
[0018]
As described above, when dry cleaning is performed by placing a substrate that is hardly etched by plasma of halogen gas such as an alumina substrate on a substrate mounting portion such as an electrostatic chuck, it is necessary to remove the adhering in the chamber. There is a problem that deposits are likely to re-adhere on the alumina substrate. Conventionally, in a dry etching apparatus that generates plasma by applying both high-frequency power for plasma generation and bias power, such as ICP, cleaning is performed without applying bias power when dry cleaning is performed. It was.
[0019]
As a result of earnest research focusing on this point, the inventor of the present application has not only generated plasma by applying high-frequency power for plasma generation when performing dry cleaning, but also applied bias power to the cleaning substrate side. It has been found that this problem can be solved by performing dry cleaning in the applied state.
[0020]
In other words, by applying bias power to the dry cleaning substrate side, a negative self-bias is formed on the dry cleaning substrate side, and as a result, positive ions in the plasma enter the surface of the dry cleaning substrate with a predetermined energy. Is done. For this reason, even if the deposit adhered in the chamber is deposited again on the alumina substrate, the deposited deposit can be removed by the sputtering effect of ions.
[0021]
Moreover, the portion of the dry cleaning substrate exposed to the plasma is made of a material such as alumina or silicon carbide (SiC) that is hardly etched by the dry cleaning gas plasma (a gas containing a halogen atom). Unlike a silicon substrate or a quartz substrate, there is no possibility that the reaction product accumulates in the chamber and causes generation of particles. In addition, dry cleaning can be performed efficiently in a short time without fear of a decrease in the cleaning rate of deposits adhering to the chamber.
[0022]
As described above, when performing dry cleaning, a substrate that is hardly etched by dry cleaning gas plasma is used as a dry cleaning substrate, and not only high frequency power for plasma generation is applied, but also on the dry cleaning substrate side. By applying the bias power, it is possible to efficiently remove deposits adhering to the chamber and reduce particles.
[0023]
In the dry cleaning method described above, the main part of the dry cleaning substrate other than the part exposed to the plasma is preferably made of a semiconductor or a conductor.
[0024]
When the dry cleaning substrate is made of an insulator such as alumina over the entire substrate, the bias power applied to the dry cleaning substrate is likely to be non-uniform within the substrate. The case where an object cannot be removed efficiently is assumed.
[0025]
For this reason, by making the main part other than the part exposed to the plasma a semiconductor or a conductor, the bias power can be applied uniformly over the entire dry cleaning substrate. It is possible to efficiently remove deposits that reattach to the surface.
[0026]
In the dry cleaning method described above, after the first dry cleaning is performed, the second dry cleaning may be performed by using a plasma of a second cleaning gas different from the first cleaning gas.
[0027]
It is assumed that even if the first dry cleaning is performed with the plasma of the first dry cleaning gas, the deposited deposits in the chamber cannot be completely removed. For this reason, after the first dry cleaning is performed, the second dry cleaning may be performed using plasma of a second cleaning gas different from the first cleaning gas. At this time, for example, by using a gas corresponding to an etching gas as the second cleaning gas, it is convenient from the viewpoint of suppressing fluctuations in etching characteristics such as an etching rate and a selection ratio before and after dry cleaning.
[0028]
The first cleaning gas is a gas containing fluorine atoms, and the second cleaning gas is a gas containing bromine atoms.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0032]
FIG. 1 is a cross-sectional view showing a dry etching apparatus used in a dry cleaning method according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing how a FeRAM ferroelectric capacitor is formed using the dry etching apparatus of FIG. FIG. 3 is a process flowchart according to the dry cleaning method of the present invention.
[0033]
First, a dry etching apparatus used in the dry cleaning method of the embodiment of the present invention will be described. As shown in FIG. 1, an ICP (Inductively Coupled Plasma) type of dry etching apparatus 1 is shown as an example.
[0034]
The dry etching apparatus 1 includes a chamber 31 including a reaction chamber 31a and an exhaust chamber 31b, and a wafer stage 32 is disposed in the reaction chamber 31a. The wafer stage 32 has a structure in which an electrostatic chuck 32b (substrate mounting portion) is disposed on a heater 32a, and a semiconductor substrate 30 to be etched is mounted on the electrostatic chuck 32b. The electrostatic chuck 32b is connected to a bias high-frequency power source 33 for applying bias power.
[0035]
Further, a substantially cylindrical deposition preventing plate 34 surrounding the region including the wafer stage 32 is disposed in the chamber 31, and the upper portion of the deposition preventing plate 34 is closed by a quartz plate 34a. The space inside the deposition preventing plate 34 becomes a reaction chamber 31a. An antenna coil 36 is mounted on the quartz plate 34a, and a high frequency power source 35 for plasma generation is connected to the antenna coil 36.
[0036]
A gas introduction pipe 40 is connected to a predetermined portion of the chamber 31, and the gas introduction pipe 40 is inserted into the reaction chamber 31a. A predetermined etching gas, cleaning gas, or the like is introduced into the reaction chamber 31a, and high-frequency electric power is applied from the high-frequency power source 35 to the antenna coil 36 to induce a high-frequency electric field in the reaction chamber 31a by electromagnetic induction coupling. Plasma is generated in the reaction chamber 31a.
[0037]
Further, an exhaust chamber 31b is provided adjacent to the reaction chamber 31a via the deposition preventing plate 34, and an opening 34b is formed in the deposition preventing plate 34. An exhaust pipe 31x is connected to the lower part of the exhaust chamber 31b, and reaction products generated by etching or dry cleaning are exhausted to the exhaust pipe 31x side through the opening 34b of the deposition preventing plate 34. Yes.
[0038]
A load lock chamber 38 is provided adjacent to the reaction chamber 31a on the opposite side of the exhaust chamber 31b via a gate valve 37. A wafer transfer port 34d that is opened and closed by a shutter 34c is provided in the deposition preventing plate 34 on the load lock chamber 38 side.
[0039]
The dry etching apparatus 1 is basically configured as described above. The inductively coupled plasma (ICP) induces a high-frequency electric field in the reaction chamber 31a held in vacuum by electromagnetic inductive coupling from the antenna coil 36, and turns the reaction gas introduced into the reaction chamber 31a into plasma. Therefore, high-density plasma can be generated with a large diameter without the need for a magnetic field.
[0040]
Although the ICP type is exemplified as the dry etching apparatus 1, a TCP (Transfer Coupled Plasma) type or an ECR (Electron Cyclotron Resonance) type may be used.
[0041]
Next, a dry cleaning method according to an embodiment of the present invention will be described with reference to the process flowchart of FIG. 3 as appropriate. Further, the process of forming the FeRAM ferroelectric capacitor of FIG. 2 will be described by way of example.
[0042]
First, in S1 of FIG. 3, a predetermined number of lots (for example, 25 pieces per lot) are etched using the dry etching apparatus 1.
[0043]
The structure of each wafer in the lot related to the etching process for forming the FeRAM ferroelectric capacitor is as follows. That is, as shown in FIG. 2A, on the insulating film 12 formed above the semiconductor substrate 30, a first metal film 14 made of a Pt film or the like in order from the bottom, lead zirconate titanate (PZT: Pb (Zr, Ti) O _Three ) Ferroelectric film 16 made of film, IrO _X A mask 20 made of a resist or the like formed in a capacitor shape is formed on the second metal film 18 made of a film or the like and the second metal film.
[0044]
Next, the semiconductor substrate 30 having the above-described structure is transported and placed on the electrostatic chuck 32b of the reaction chamber 31a of the dry etching apparatus 1 of FIG. Subsequently, an etching gas made of, for example, a mixed gas of chlorine and oxygen is supplied from the gas introduction pipe 40 of the dry etching apparatus 1 so that the inside of the chamber 31 is adjusted to a predetermined gas pressure.
[0045]
Thereafter, a predetermined high frequency power is applied from the high frequency power source 35 to the antenna coil 36 to generate an induction electromagnetic field in the chamber 31, and a predetermined bias power is applied from the bias high frequency power source 33 to the electrostatic chuck 32 b. The etching gas is turned into plasma.
[0046]
As a result, as shown in FIG. 2B, the second metal film 18, the ferroelectric film 16, and the first metal film 14 other than the mask 20 are sequentially etched. By this etching, the capacitor 22 is formed, the second metal film 18 becomes the upper electrode 18a of the capacitor 22, the ferroelectric film 16 becomes the dielectric film 16a of the capacitor 22, and the first metal film 14 becomes the lower part of the capacitor 22. It becomes the electrode 14a.
[0047]
At this time, the film to be etched is IrO _X Since the reaction product of the film to be etched and the etching gas has low volatility, etching proceeds mainly by sputtering reaction. For this reason, reaction products containing Pt, Ir, and the like are likely to adhere to the inner wall of the chamber 31, the deposition preventing plate 34, the quartz plate 34a, and the like.
[0048]
FIG. 4A is a cross-sectional view showing a state in which deposits adhere to the deposition plate or quartz plate in the reaction chamber. As shown in FIG. 4A, for example, in the process of forming the FeRAM capacitor 22, the deposit 21 containing Pt, Ir, or the like adheres to the deposition preventing plate 34, the quartz plate 34a, or the like. Then, the deposit 21 is accumulated as the number of processed sheets increases, and then the deposit 21 is peeled off to cause generation of particles. In order to prevent this, it is necessary to periodically dry clean the inside of the chamber 31 of the dry etching apparatus 1 to remove the deposit 21.
[0049]
For example, when the dry etching apparatus 1 is applied to a process of forming a FeRAM ferroelectric capacitor, dry cleaning may be performed for each lot (25 sheets).
[0050]
Next, a method for removing the deposit 21 attached in the chamber 31 of the dry etching apparatus 1 by dry cleaning will be described. First, the dry cleaning substrate will be described. 5 and 6 are cross-sectional views showing a dry cleaning substrate according to an embodiment of the present invention. When dry cleaning is performed by plasmaizing the dry cleaning gas, if the electrostatic chuck 32b is exposed, the electrostatic chuck 32b may be damaged by the plasma and destroyed.
[0051]
For this reason, when performing dry cleaning, it is necessary to place the dry cleaning substrate on the electrostatic chuck 32b to protect the electrostatic chuck 32b from plasma. When performing dry cleaning for such a purpose, a dry cleaning substrate is required.
[0052]
As described above, when an alumina substrate that is hardly etched by halogen gas plasma is used as the dry cleaning substrate, the problem that occurs when using a silicon substrate or quartz substrate that is easily etched by halogen gas plasma is solved. However, there remains a problem that the deposit 21 adhering to the chamber 31 easily reattaches on the alumina substrate.
[0053]
The purpose of applying bias power to the electrostatic chuck 32b side in the ICP type dry etching apparatus 1 is to adjust the etching shape, the selectivity with respect to the mask or the base film, and the like when the object to be etched is etched. Therefore, conventionally, there is no need to apply a bias power when performing dry cleaning.
[0054]
As a result of intensive research focusing on this point, the inventor of the present application has not only applied the high frequency power from the high frequency power supply 35 to the antenna coil 36 to generate plasma when performing dry cleaning, but also applied to the electrostatic chuck 32b. It has been found that the above-described problems can be solved by performing dry cleaning with bias power applied.
[0055]
That is, by applying a bias power to the electrostatic chuck 32b, a negative self-bias is formed on the electrostatic chuck 32 side. As a result, positive ions in the plasma are accelerated to the electrostatic chuck 32b side, and the semiconductor substrate 30 The light is incident on the surface with a predetermined energy. For this reason, even if the deposit 21 adhering in the chamber 31 is redeposited on the alumina substrate, the deposit adhering again by the sputtering action of ions can be removed.
[0056]
In addition, since alumina has a characteristic that it is hardly etched by plasma of halogen gas, unlike a silicon substrate or a quartz substrate, there is no possibility that reaction products accumulate in the chamber 31 and cause generation of particles.
[0057]
In this way, by using an alumina substrate that is hardly etched by halogen gas plasma as a dry cleaning substrate and applying high-frequency power for plasma generation, bias power is applied to the electrostatic chuck 32b side. The deposit 21 adhering in the chamber 31 can be efficiently removed to reduce particles.
[0058]
In addition to the alumina substrate, a silicon carbide (SiC) substrate having characteristics that are hardly etched by halogen gas plasma may be used as the dry cleaning substrate.
[0059]
In addition to the alumina substrate and the SiC substrate, as shown in FIG. 5, a dry film in which an alumina film 24 (or SiC film) hardly etched by halogen gas plasma is formed on an insulating substrate 23 such as a quartz substrate. A cleaning substrate 26 can be used.
[0060]
Here, when using the alumina substrate, the SiC substrate, or the insulating substrate 23 having the alumina film 24 (or SiC film) formed on the surface as a dry cleaning substrate, the main part including the portion that comes into contact with the electrostatic chuck 32b is Since it is made of an insulator, the applied bias power is likely to be non-uniform in the dry cleaning substrate, and it is assumed that the deposited deposit cannot be removed efficiently.
[0061]
For this reason, it is preferable that the part other than the part exposed to the plasma of the dry cleaning substrate is made of a semiconductor or a conductor.
[0062]
That is, as shown in FIG. 6, preferably, a dry etching substrate 26a in which an alumina film 24 (or SiC film) that is hardly etched by halogen gas plasma is formed on a conductive substrate 25 (or a semiconductor substrate). May be used. Accordingly, in the dry cleaning substrate 26a of FIG. 6, the conductive substrate 25 (or semiconductor substrate), which is the main part thereof, comes into contact with the electrostatic chuck 32b. Bias power is applied. As a result, it becomes possible to efficiently remove the deposits reattached on the dry cleaning substrate 26au.
[0063]
It should be noted that the main part including the part in contact with the electrostatic chuck 32b being a semiconductor or a conductor is convenient also from the viewpoint of increasing the electrostatic adsorption force between the electrostatic chuck 32b and the dry cleaning substrate.
[0064]
The alumina film 24 is formed on the conductive substrate 25 (or semiconductor substrate) by thermal spraying, sputtering or CVD. Further, when an SiC film is formed instead of the alumina film 24, the film is formed by sputtering, CVD or the like. In addition, a silicon substrate or the like can be used as the semiconductor substrate, and a metal substrate such as an aluminum substrate can be used as the conductive substrate. Alternatively, an aluminum substrate having an alumina film on one surface by oxidizing one surface of the aluminum substrate may be used.
[0065]
As described above, the dry cleaning substrate used in the dry cleaning method of the present embodiment may be a substrate made of a material (alumina or SiC) that is hardly etched by halogen gas plasma at least in a portion exposed to plasma. A substrate whose main part is made of a semiconductor or a conductor is preferable.
[0066]
Next, the process proceeds to S2 in FIG. 3 to perform the first dry cleaning. FIG. 4B is a cross-sectional view showing how the reaction chamber is dry cleaned. A dry cleaning substrate (for example, 26a in FIG. 6) having the above-described configuration is prepared, transported into the dry etching apparatus 1, and placed on the electrostatic chuck 31 (substrate placing portion).
[0067]
At this time, the exposed surface of the conductive substrate 25 of the dry cleaning substrate 26a is on the electrostatic chuck 32b side, and the exposed surface of the alumina film 24 is a surface exposed to plasma so as to be on the electrostatic chuck 32b. Placed. Of course, the dry cleaning substrate 26 shown in FIG. 5 may be used, or an alumina substrate or a SiC substrate may be used.
[0068]
Thereafter, for example, sulfur hexafluoride (SF) is introduced from the gas introduction pipe 40 of the dry etching apparatus 1. ₆ ) At a flow rate of 1000 sccm, and the chamber 31 is adjusted to have a gas pressure of 12.5 Pa. Subsequently, 2700 W of electric power is supplied from the high frequency power source 35 to the antenna coil 36, and 300 W of electric power is supplied from the bias high frequency power source 33 to the electrostatic chuck 32b. ₆ First dry cleaning is performed for 30 minutes by generating plasma.
[0069]
As a result, as shown in FIG. 4B, the deposit 21 containing Pt, Ir, etc. adhering to the deposition preventing plate 34, the quartz plate 34a, etc. is SF. ₆ It is removed by reacting with active fluorine in the plasma. Moreover, since bias power is applied to the electrostatic chuck 32b, even if the deposit 21 is reattached on the dry cleaning substrate, it is blown off by the incident ions, and the surface is free of particles. This completes the dry cleaning.
[0070]
Furthermore, since the portion of the dry cleaning substrate exposed to the plasma is made of an alumina film or SiC film, SF ₆ It hardly reacts with the active fluorine in the plasma, and the generation of reaction products as a particle source is suppressed as much as possible. In addition, since excessive consumption of the dry cleaning gas is suppressed, the etching rate of the deposit 21 is stabilized, so that dry cleaning can be performed efficiently in a short time.
[0071]
The gas used in the first dry cleaning is SF. ₆ But NF _Three , CF _Four Or C ₂ F ₆ You may use fluorine-type gas, such as. In addition, other gases such as an inert gas, a chlorine-based gas, or a bromine-based gas may be added to the fluorine-based gas as necessary. That is, as the first cleaning gas, a gas having a gas atmosphere containing at least fluorine atoms may be used.
[0072]
Next, the process proceeds to S3 in FIG. 3, and the second dry cleaning (seasoning) is performed after the first dry cleaning. In the second dry cleaning, deposits in the chamber 31 that could not be removed by the first dry cleaning are removed, and the reaction chamber 31a of the chamber 31 is previously etched before returning to S1 and performing lot processing. This is done to keep the atmosphere of gas plasma. This prevents fluctuations in etching characteristics such as the etching rate and the selectivity with respect to the mask and the base film before and after dry cleaning.
[0073]
That is, SF ₆ Instead of using a plasma of a mixed gas of chlorine and oxygen, the dry cleaning substrate 26a is placed on the electrostatic chuck 32b by the same method as the first dry cleaning, and the second dry cleaning is performed. . For example, chlorine (Cl ₂ ): 10 sccm, oxygen (O ₂ ): 40 sccm, pressure: 0.4 Pa, high frequency power for plasma generation: 800 W, power for bias: 0 W, processing time: 10 minutes.
[0074]
In the second dry cleaning, a first dry cleaning gas (for example, SF) ₆ ) Different from the second cleaning gas (for example, Cl ₂ And O ₂ Therefore, the deposit 21 in the chamber 31 that could not be removed by the first dry cleaning is removed. Similarly to the first dry cleaning, the portion of the dry cleaning substrate 26a exposed to the plasma is made of an alumina film or a SiC film, so that Cl ₂ And O ₂ Reaction with the plasma of the mixed gas and the generation of reaction products serving as particle sources is minimized.
[0075]
In the second dry cleaning described above, a condition in which the bias power is not applied is illustrated, but a bias power may be applied. Further, as the second cleaning gas, Cl ₂ And O ₂ HBr or HBr and O instead of the mixed gas ₂ A mixed gas or the like may be used. Moreover, you may make it add the gas containing an inert gas and a fluorine atom as needed. That is, as the second cleaning gas, a gas having a gas atmosphere containing at least chlorine atoms or bromine atoms may be used.
[0076]
Note that, from the viewpoint of suppressing variation in etching characteristics before and after dry cleaning, the gas applied to the second dry cleaning (seasoning) is preferably matched to the gas atmosphere of the etching conditions.
[0077]
Further, the second dry cleaning (seasoning) may be omitted, or conversely, the second dry cleaning (seasoning) described above may be repeatedly performed. By repeatedly performing the second dry cleaning (seasoning), the generation of particles in the dry etching apparatus 1 can be further reduced.
[0078]
In the second dry cleaning (seasoning), if a silicon substrate or a quartz substrate is used as a dry cleaning substrate, particles are not reduced. This is because the silicon substrate and the quartz substrate are etched to some extent by the chlorine-based gas or bromine-based gas, so that the reactive substance adheres to the chamber and becomes a particle source.
[0079]
Next, returning to S1 in FIG. 3, for example, one lot processing is performed, then the process proceeds to S2 to perform the first dry cleaning again, and then proceeds to S3 to perform the second dry cleaning again. In this way, after etching a predetermined number of lots (for example, 20 to 30 lots), the chamber 31 of the dry etching apparatus 1 is opened to the atmosphere, and the inner wall of the chamber 31, the deposition plate 34, the quartz plate 34 a, etc. May be wet-cleaned with chemicals.
[0080]
As described above, the dry cleaning method of this embodiment can be performed.
[0081]
The inventor of the present application investigated the dependency of the number of particles on the number of processed wafers in order to confirm the effect of the dry cleaning method of the above-described embodiment. FIG. 7 shows the dependency of the number of particles on the number of wafers processed when the dry cleaning method of the embodiment of the present invention is performed. In the particle check method, a particle check silicon substrate is transported onto the electrostatic chuck 32b of the chamber 31 to generate an argon plasma, and the silicon substrate is unloaded. (The diameter was 0.2 μm or more) was counted.
[0082]
The data in which the number of wafers processed on the horizontal axis in FIG. 7 is zero is the result of performing a particle check after wet cleaning the chamber 31 of the dry etching apparatus 1, the deposition prevention plate 34, the quartz plate 34a, and the like. Prior to processing, 160 particles were counted.
[0083]
Subsequently, a predetermined wafer to be etched is continuously etched in units of 25 under predetermined etching conditions, and then the particle check is performed after the first and second dry cleaning methods of the present embodiment described above are executed. went. Subsequently, the transition of the number of particles was investigated by repeating the process until the total number of sheets 275 was processed.
[0084]
From 25 sheets to 100 sheets, 100 to 200 particles were counted. From 125 sheets to 275 sheets, about 25 to 100 particles were counted.
[0085]
As described above, even when 275 wafers are processed, the number of particles is 200 or less, and it was confirmed that the dry cleaning method of this embodiment has a high effect of suppressing the generation of particles.
[0086]
In addition, when an alumina substrate was used as the dry cleaning substrate and the first dry cleaning was performed without applying bias power, 10000 or more particles were counted.
[0087]
Next, it was confirmed how the number of particles changed when a quartz substrate was used instead of an alumina substrate as a dry cleaning substrate. FIG. 8 shows the dependence of the number of particles on the number of processed wafers when a quartz substrate is used as the dry cleaning substrate.
[0088]
Using a quartz substrate instead of an alumina substrate, the dependency of the number of particles on the number of wafers processed was investigated in the same manner as the experiment method performed on the number of particles processed on wafers in FIG. The second dry cleaning (seasoning) was not performed.
[0089]
As shown in FIG. 8, as a whole, unlike the case of using an alumina substrate, the number of particles tends to increase as the number of processed wafers increases. When 75 wafers are processed, the number of particles exceeds 1000, and after 200 wafers are processed, the number of particles becomes 10000 or more. As described above, the quartz substrate is SF. ₆ It is presumed that particles are increased due to the reaction product adhering to the inside of the chamber.
[0090]
Next, SF ₆ The etching rate of the silicon oxide film was investigated under the first dry cleaning conditions using In this embodiment, since the bias power is applied in the first dry cleaning, the etching rate of quartz tends to increase. In the dry etching apparatus 1 shown in FIG. 1, a quartz plate 34a is present at the upper part of the chamber 31, and an EPD is provided on the side wall of the reaction chamber 31a of the chamber 31 so that an end point detector (EPD) monitors plasma emission. A window is provided, and quartz glass is installed in this window.
[0091]
Therefore, in order to predict the wear of these quartz in the dry cleaning method of this embodiment, the silicon substrate on which the silicon oxide film is formed is placed in the vicinity of the EPD window and in the region on the exhaust chamber 31b side of the reaction chamber 31a. The silicon oxide film etching rate was investigated under various cleaning conditions. FIG. 9 shows the etching rate of the silicon oxide film under various dry cleaning conditions according to the embodiment of the present invention.
[0092]
As shown in FIG. 9, under the reference conditions (no bias power application), the etching rate of the silicon oxide film was about 50 nm / min near the EPD window and about 55 nm / min on the exhaust chamber side.
[0093]
Under condition 1 with bias power application, the voltage increased to about 62 nm / min in the vicinity of the EPD window and to about 115 nm / min on the exhaust chamber side. In addition, for condition 1, SF ₆ Under the condition 2 where the flow rate of the gas was increased to 550 sccm and the pressure was increased to 5 Pa, there was no change of 50 nm / min near the EPD window, and 90 nm / min on the exhaust chamber side.
[0094]
Furthermore, SF for condition 2 ₆ Under the condition 3 where the flow rate of the gas was increased to 850 sccm and the pressure was increased to 7 Pa, the flow rate increased to 80 nm / min in the vicinity of the EPD window and increased to about 122 nm / min on the exhaust chamber side.
[0095]
For condition 3, SF ₆ In condition 4 where the flow rate was increased to 1100 sccm and the pressure was increased to 10 Pa, it further increased to about 94 nm / min near the EPD window, and further increased to about 132 nm / min on the exhaust chamber side.
[0096]
As described above, when bias power is applied, the etching rate of the silicon oxide film tends to increase. However, the etching rate is greatly increased so that the consumption of quartz is significantly more intense than in the reference condition (no bias power is applied). It turns out that doesn't happen. That is, by applying the dry cleaning method of the present embodiment, there is no problem such as frequent replacement of the quartz jig of the dry etching apparatus 1.
[0097]
(Appendix 1) A dry cleaning method of a dry etching apparatus of a type that performs etching by generating plasma by applying high frequency power for plasma generation and power for bias to a predetermined gas atmosphere,
A dry cleaning substrate having at least a portion exposed to plasma made of alumina or silicon carbide is placed on a substrate placement portion in a chamber of the dry etching apparatus, and a first cleaning gas is introduced into the chamber; A dry cleaning method comprising performing the first dry cleaning by generating the plasma by applying the high frequency power for plasma generation and the high frequency power for bias.
[0098]
(Appendix 2) The dry cleaning substrate is:
A substrate selected from the group of a semiconductor substrate, a conductive substrate and an insulating substrate;
The dry cleaning method according to claim 1, further comprising an alumina film or a silicon carbide (SiC) film formed on the substrate.
[0099]
(Additional remark 3) The dry cleaning method of Additional remark 1 characterized by the main parts other than the part exposed to the said plasma of the said substrate for dry cleaning consisting of a semiconductor or a conductor.
[0100]
(Additional remark 4) The dry cleaning method of Additional remark 1 characterized by the main parts other than the part exposed to the said plasma of the said dry-cleaning board | substrate consisting of an insulator.
[0101]
(Supplementary note 5) The dry cleaning method according to any one of supplementary notes 1 to 4, wherein the first cleaning gas is a gas containing a fluorine atom.
[0102]
(Supplementary note 6) Any one of Supplementary notes 1 to 5, wherein after the first dry cleaning is performed, a second dry cleaning is performed with a plasma of a second cleaning gas different from the first cleaning gas. The dry cleaning method according to one item.
[0103]
(Supplementary note 7) The dry cleaning method according to supplementary note 6, wherein the second cleaning gas is a gas containing a chlorine atom or a gas containing a bromine atom.
[0104]
(Supplementary Note 8) A substrate selected from the group of a semiconductor substrate, a conductive substrate, and an insulating substrate;
A dry cleaning substrate comprising an alumina film or a silicon carbide film formed on the substrate.
[0105]
(Supplementary note 9) The dry cleaning substrate according to supplementary note 8, wherein the substrate is the semiconductor substrate made of silicon or the conductive substrate made of metal.
[0106]
【The invention's effect】
As described above, according to the present invention, when dry cleaning is performed, a dry cleaning substrate whose portion exposed to plasma is made of alumina or silicon carbide is placed on the substrate placement portion in the chamber. In addition to generating plasma by applying high-frequency power for plasma generation, dry cleaning is performed in a state where bias power is applied to the cleaning substrate side.
[0107]
For this reason, even if the deposit adhering in the chamber is redeposited on the dry cleaning substrate, the deposit adhering again by the sputtering action of ions can be removed. Moreover, since the portion of the dry cleaning substrate exposed to the plasma is made of a material that is hardly etched by the dry cleaning gas plasma such as alumina or silicon carbide (SiC), the silicon substrate, the quartz substrate, etc. Unlike the case, the reaction product does not accumulate in the chamber and cause generation of particles.
[0108]
By doing so, it is possible to efficiently remove deposits adhering in the chamber of the dry etching apparatus and reduce particles.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a dry etching apparatus used in a dry cleaning method according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an example in which the dry etching apparatus of FIG. 1 is applied to a process of forming a FeRAM ferroelectric capacitor.
FIG. 3 is a process flowchart according to the dry cleaning method of the embodiment of the present invention.
4A is a cross-sectional view showing a state in which deposits adhere to a deposition plate or a quartz plate in a reaction chamber, and FIG. 4B is a cross-sectional view showing a state in which the reaction chamber is dry-cleaned. is there.
FIG. 5 is a cross-sectional view showing a first example of a dry cleaning substrate according to an embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a second example of a dry cleaning substrate according to an embodiment of the present invention.
FIG. 7 shows the dependence of the number of particles on the number of wafers processed when the dry cleaning method of the embodiment of the present invention is performed.
FIG. 8 shows the dependency of the number of particles on the number of wafers processed when a quartz substrate is used as the dry cleaning substrate.
FIG. 9 shows an etching rate of a silicon oxide film in the dry cleaning method of the embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Dry etching apparatus, 12 ... Insulating film, 14 ... 1st metal film, 16 ... Ferroelectric film, 18 ... 2nd metal film, 20 ... Mask, 21 ... Deposit, 23 ... Insulating substrate, 24 ... Alumina Film (or SiC film), 25 ... conductive substrate (or semiconductor substrate), 26, 26a ... dry cleaning substrate, 30 ... semiconductor substrate, 31 ... chamber, 31a ... reaction chamber, 31b ... exhaust chamber, 31x ... exhaust pipe 32 ... Wafer stage, 32a ... Heater, 32b ... Electrostatic chuck, 33 ... High frequency power supply for bias, 34 ... Depositing plate, 34a ... Quartz plate, 34b ... Opening, 34c ... Shutter, 34d ... Wafer transfer port, 35 ... high frequency power supply, 36 ... antenna coil, 37 ... gate valve, 38 ... load lock chamber, 40 ... gas introduction pipe.

Claims (5)

A dry cleaning method of a dry etching apparatus of a type that performs etching by generating plasma by applying high frequency power for plasma generation and high frequency power for bias to a predetermined gas atmosphere,
A dry cleaning substrate having at least a portion exposed to plasma made of alumina or silicon carbide is placed on a substrate placement portion in a chamber of the dry etching apparatus, and a first cleaning gas is introduced into the chamber; Applying the first high-frequency power for plasma generation and the high-frequency power for bias to generate the plasma to perform first dry cleaning;
After performing the first dry cleaning, a second dry cleaning is performed with a plasma of a second dry cleaning gas different from the first dry cleaning gas,
In the second dry cleaning, the second high frequency power for plasma generation is applied, and the high frequency power for bias is not applied. 2. The dry cleaning method according to claim 1, wherein at least a portion in contact with the substrate mounting portion of the dry cleaning substrate is made of a semiconductor or a conductor.   The dry cleaning method according to claim 1, wherein the first cleaning gas is a gas containing fluorine atoms.   The dry cleaning method according to claim 1, wherein the second cleaning gas is a gas containing bromine atoms.   The dry cleaning method according to claim 2, wherein the high-frequency power for bias is supplied to the dry cleaning substrate.

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